Batt insulation is commonly manufactured by fiberizing mineral fibers from a molten mineral bath by forcing them through a spinner rotating at a high number of revolutions per minute. The fine fibers are then contacted by a pressurized hot gas to draw the fibers to a useable diameter and length. The fibers are typically sprayed with a phenolic resin binder. The fibers are then collected and distributed on a conveyor to form a mat. The resin is then cured in a curing oven. The mat is then sliced into lengthwise strips having desired widths and chopped into individual batts. In some cases, a facing material, such as Kraft paper coated with a bituminous material or other vapor retarder, is added to the mat prior to the cutting step.
One of the known problems associated with installing glass fiber insulation materials is that they generate glass particle dust, which can be a cause of irritation to workers by contact with skin and eyes or by respiration. One way to reduce glass dust is to encapsulate insulation batts with a facing that reduces dust, but which is porous, and vapor permeable. WO94/29540, assigned to Owens Corning Fiberglas Corporation, teaches a polymeric facing which is adhered to one or both major surfaces of the batt with a fastening means, such as a small amount of adhesive material. The adhesive material is of a sufficiently small amount so as to enable the insulation batt not to exceed a flame spread rating of 25 using the ASTM E-84 flame spread test. The adhesive should be applied in sufficient quantity to bond the facing to the mineral fiber batt and enable the batt to be picked up and handled by the facing. The facings described in this reference are suggested to be a polypropylene or polyethylene material, which is adhered, stuck or heat sealed to the major surfaces of the batt.
Knapp et al., U.S. Pat. No. 5,848,509 commonly assigned with the instant application, teaches encapsulated glass fiber insulation within a nonwoven covering material. The nonwoven covering is disposed over the top surface of a mineral fiber core and extends adjacent the side surfaces. The covering is preferably formed from a web of nonwoven material, such as polyester, polypropylene, polyethylene or rayon, and is preferably applied to the top and sides of the glass fiber mat with a hot melt or suitable adhesive.
In order to provide insulation mats with encapsulated nonwoven coverings or films, quantities of adhesive must also be stored for adhering these coverings to batt insulation. Many adhesives and glues have a limited shelf life. Additionally, spraying these adhesives on batt surfaces requires constant cleanup and maintenance of manufacturing equipment and the work area. Still further, prior art encapsulated mats that utilize synthetic nonwoven facing layers such as polyester have proved difficult to cut in the field.
Accordingly, there remains a need for an encapsulated or faced insulation material which can be made less expensively, but which still reduces dust and permits air evacuation when the insulation product is compressed for packaging and which provides for improved ease of installation.